GARDENING Australia presenter and environmental scientist Josh Byrne will host a series of free workshops next month to help people care for their garden, while also caring for the Swan River.

Mr Byrne said the Swan Canning River system was being negatively affected by the large amount of nitrogen and phosphorus entering the river each year, with amounts more than double what it could safely receive.

He said the Ellen Brook catchment was one of the most significant contributors of nutrients in the vicinity and on the Swan Coastal Plain, creating 71 tonnes of nitrogen and 10 tonnes of phosphorus to the Swan River each year.

About 250 tonnes of nitrogen and 26 tonnes of phosphorus enter the Swan River each year, which can lead to algal blooms, deoxygenation and fish deaths as well as cause skin irritation to humans.

Mr Byrne said research showed the main source of nitrogen entering the river was from the residential sector through fertiliser application.

“This isn’t about tearing up your lawns and covering everything with mulch,” he said.

“There are simple and cost effective steps we can take to reduce nutrient pollution and it starts with building healthy soil and only feeding plants what they need, when they need it.”

The free Your Garden with Josh Byrne 2018 workshops will run on May 2 in Guildford, May 9 in Harrisdale and May 16 in Ellenbrook.